Abstract
The amounts of α-lipoic acid in whole blood of man and rat were estimated by microbiological assay with Streptococcus faecalis after the oral administration of TATD and lipoamide in a large dose. In rats, the lipoic acid values in the blood estimated with time after the administration were highest at 15 minutes in both cases. The 15 minutes value of TATD loading showed far larger ones than those of lipoamide loading at same molar doses of 5,20 mg equivalent to lipoic acid per kg body weight, while at a dose of 80 mg equivalent, lipoamide loading gave a larger value of lipoic acid in blood than TATD loading. In man, the amounts of blood lipoic acid of TATD loading were 14 and 8 times as much as those of lipoamide loading at 15 and 30 minutes after the administrations, respectively. These findings suggested the difference of absorption mechanism between TATD and lipoamide and the superiority of TATD absorption in a certain dose. This assumption was confirmed by the human experiments of TATD-^<35>S and lipoic acid-^<35>S administration in which ^<35>S excretion in 24 hour-urine after TATD administration showed 70% of TATD-^<35>S administered equivalent to 100 mg of lipoic acid while the urinary ^<35>S excretion after lipoic acid-^<35>S administration was 40%. However, lipoic acid amounts responded to Stc. faecalis in 24 hour-urine were only 0.4% of TATD-^<35>S and 0.3% of lipoic acid-^<35>S administered.
